The invention relates to a method for controlling an rpm-converting engaging device of a motor vehicle driven by an internal combustion engine, preferably an accelerator pedal or a throttle, whereby the rpm difference based on the input rpm, i.e., the engine rpm nmot(t), of an engaging device is controllable between the input rpm of the engaging device and its output rpm, i.e., the transmission input rpm ne(t).
In motor vehicles with a manually actuated engaging device (friction clutch), by suitable actuation of the accelerator and clutch pedals the driver can structure an engaging process nearly freely within the physical limits of the system. This enables him to adjust the dynamics of the engaging process individually to his driving style or to a prevailing driving or traffic situation.
The driver will therefore adjust the engaging rpm of the engine and the slip of the clutch using the accelerator pedal and clutch in such a way that the engine generates the corresponding engaging torque or the corresponding engaging power that is correct for the situation.
The correct, and especially low-wear, control of the accelerator and clutch pedals by the driver however requires firstly a certain amount of skill and concentrated action; on the other hand, especially in so-called stop-and-go traffic, for example in densely populated areas and in heavy traffic, the constant actuation of the accelerator and clutch pedals is quite fatiguing.
Therefore, in the past, automatic engaging devices were developed for motor vehicles. These can be divided roughly into two groups:
engaging devices which act automatically without additional control means, for example centrifugal clutches and hydrodynamic torque converters, and PA1 engaging devices controlled separately by means of auxiliary energy, for example hydraulically actuated friction clutches or electromagnetic powder clutches.
While in the engaging devices of the first group the torque or power transmitted depends primarily upon the slip in the engaging device, and/or the input rpm and the effect of these parameters on the torque or power is largely determined by the structural design, the engaging devices of the second group are largely flexible both in terms of the influential parameters as well as their effect.
On the other hand, the engaging devices of the first group are relatively problem-free as regards wear and heating, while the overly-free design of the control engaging devices in the second group has limits placed upon it in this regard: monitoring devices for wear and heating are therefore nearly unavoidable.
In order to keep the cost of controls for engaging devices of the second group as low as possible, these controls are frequently so designed that they simulate a centrifugal clutch or hydrodynamic torque converter in their behavior. In this manner, however, the behavior of such a system is once again largely fixed.
From European Patent document EP 0 276 022 A2, a control device is known for a vehicle clutch which, for the purpose of controlling the starting operation, determines the rotational speeds of the driving and the rotational speeds of the driven parts of the clutch and, as a function thereof, controls the clutch engagement such that this clutch engagement follows a preset clutch engagement.
Taking its departure from this prior art, the goal of the invention is to provide a method for automatic control of a torque-converting engaging device for a motor vehicle, which adjusts itself automatically to the driving behavior of a driver of the motor vehicle or to a currently prevailing traffic situation and controls the engaging processes according to the situation.
The goal is achieved according to the invention by a method for controlling an rpm-converting engaging device of a motor vehicle driven by an internal combustion engine, whose engine is influenceable by a power control element, preferably an accelerator pedal or a throttle, whereby the rpm difference based on the input rpm, i.e., the engine rpm nmot (t), of an engaging device is controllable between the input rpm of the engaging device and its output rpm, i.e., the transmission input rpm ne(t). A characteristic curve is selected along which the respective rpm difference is adjusted at least during an engaging process by the engaging device indirectly or directly as a function of at least the engine rpm, corresponding to the value of a driven activity which is determined prior to the engaging process or prior to stopping the motor vehicle and which evaluates the driver's driving style or his actions caused by the traffic situation, from a family of several engaging characteristic curves.
The advantages of the invention lie primarily in the fact that a method for automatic control of a torque-converting engaging device for a motor vehicle is provided that adjusts automatically and optimally to the driving behavior of a driver of a motor vehicle or to a prevailing traffic situation and correspondingly permits engaging processes correct for the situation to proceed largely automatically.
The control according to the invention also makes it possible to control the engaging device according to relatively simple functions, whereby only parameters of the function corresponding to a driving activity determined from at least one operating parameter of the motor vehicle are varied.
This is accomplished primarily by a curve according to which an rpm differential (sak(t)) related to the input rpm, between the input rpm and the output rpm of the engaging device, is adjusted at least during one engaging process by the engaging device being adjusted indirectly or directly as a function of at least the input rpm (engine rpm nmot(t)), corresponding to the value determined prior to the engaging process or prior to the stopping of the motor vehicle, of the driving activity (SK(t)) from a family of several engaging curves (AFKi; i=1, 2, . . . , 5).
The method according to the invention is advantageously applicable to engaging devices which operate automatically without additional control means, for example centrifugal clutches and hydrodynamic torque converters (to the extent that these are controllable in their recognition or in their impressed curve, and also to engaging devices that are controlled separately by auxiliary energy, as for example electrohydraulically actuated friction clutches or electromagnetic powder clutches.
The invention will now be explained with reference to the embodiments shown in the drawings, without limitation of generality, using the example of a continuously variable transmission.